Methods for Scale-Up From a Pilot Plant to a Larger Production Facility

ABSTRACT

Methods for scale-up from a pilot plant to a larger production facility of a bimodal polymer product having a density, a melt index and melt index ration are provided herein.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit to Ser. No. 62/665,831, filed May 2,2018, the disclosure of which is hereby incorporated by reference in itsentirety.

FIELD OF THE INVENTION

The present disclosure generally relates to gas phase polyethylenepolymerization using a single catalyst system and/or a dual catalystsystem and more specifically, to methods for scale-up from a pilot plantto larger polymer production facilities.

BACKGROUND OF THE INVENTION

Pilot plants are useful in simulating larger polymer productionfacilities. In a pilot plant, an operator can experiment, investigateand troubleshoot production problems without the risk and expensesassociated with larger scale productions.

For production and control of bimodal polymer in a single reactor, theprocess conditions are varied to produce resin having a specific meltindex (MI or I2 using the 2.16 kg weight) and density. However, for abimodal or multi-modal (i.e., terpolymer) polymer, both the propertiesof each polymer as well as mixture concentration of two or more polymers(i.e., a high molecular weight polymer and a low molecular weightpolymer) are a function of the two or more types of catalysts usedsometimes referred to as a bimodal catalyst system, mixed catalystsystem, or dual catalyst system. For purposes here, these terms shall beused interchangeably to mean the same thing.

Therefore, while various reactor conditions (i.e., the partial pressuresof ethylene, hexene-1, and hydrogen, reactor temperature and residencetime) can be adjusted to provide an overall melt index and density inproduct, the mixture as defined by the split (weight % of the highmolecular weight polymer) must be consistent. If the split is notconsistent, a product having identical MI and density can be producedwith incorrect polymer property requirements.

Producing a multimodal polymer in a single reactor offers added degreesof freedom. For example, the polymer split is controlled by amount andreaction rate of each catalyst in the reactor. But this can causeuncertainties in defining the exact conditions to produce the requiredoverall polymer MI and density as well as in providing end-productproperty requirements. Currently, the actual split of the polymer cannotbe measured in a simple real-time measurement. While the bimodality ofthe polyethylene product can be analyzed by known analytical methods(i.e., GPC (Gel Permeation Chromatography)), combined with TREF(Temperature Rising Elution Fractionation) to measure the molecularweight distributions, the polymer split and the comonomer incorporation,these analytical techniques are time consuming and not typical ofmeasurements at manufacturing QC (Quality Control) laboratories whichtypically rely on standard ASTM type polymer analysis (i.e., MI,density, MIR, where MIR=I21/I2 where I21 is the MI using the 21.6 kgweight and I2 uses the 2.16 kg weight).

Prior to producing a new polyethylene composition in a commercialreactor, basic data is first developed at a smaller experimental scaleto obtain the specific reactor conditions and combinations of catalystsrequired. But, for various reasons, the scale-up from pilot plant tolarger production facilities or commercial plants cannot be perfectlyperformed. For example, when scaling-up for commercial processing,offsets in set points must be established for process conditions, eventhough abundant efforts might have been expended on calibration.

For a polymer produced with a single catalyst, this issue is not ofmajor concern because scale-up is relatively straightforward. However,with a multi-modal polymer, if the MI is too low, then it is not knownwhat to adjust because there are multiple adjustments that can be madesuch as a hydrogen off set or the polymer split. To compound matters,the polymer split might be off target due to several issues including,but not limited to: (1) the concentration of each of the bimodalcatalysts inside the reactor; (2) the effect of a particular catalystpoison or combination of poisons that might preferentially deactivateone of the catalysts relative to the other; (3) off sets in the flowmeters that are used to control the flow of each of the catalysts; (4) amultitude of variables relating to the manufacture of the catalysts;and/or (5) other reactor process conditions that might affect onecatalyst relative to the other (i.e., reactor residence time, isopentaneconcentrations, reactor temperature and ethylene partial pressure). Anychange to any of these conditions can affect the polymer MI while thepolymer product composition at target MI and density might not be whatis desired.

On the other hand, for a single catalyst system, offsets are oftendetermined when the polymer measurements are not as expected from pilotplant data. In the single catalyst system, adjusting the reactorconditions to achieve the product can be straightforward, as offsets aredetermined by the QC lab measurements of the polymer properties(including melt index, density, and melt index ratio), which allows fordecisions as to what reactor process conditions are adjusted and may bedifferent than expected from the pilot plant data. Reactor conditionscan be adjusted to achieve the correct product grade and this processcan be straightforward.

However, for the bimodal polymer, the percentage of high molecularweight polymer is unknown and may change if there are offsets in anynumber of process conditions. As such, process conditions developed inthe pilot plant or laboratory scale and adjusted upon scale-up to alarger production facilities can change the mixture composition of thebimodal polymer product.

A need exists, therefore, for new methodology to maintain the mixtureconcentration of the bimodal polymer product upon scale-up to largerproduction facilities.

SUMMARY OF THE INVENTION

Methods for scale-up from a pilot plant to a larger production facilityof a bimodal polymer product having a density and a melt index areprovided herein. In addition, the present methods can be used insubsequent commercial polyethylene manufacturing campaigns at the samecommercial scale facility or at a different location, where due to timeor similar of other off-sets, the transitioning causes uncertainties inknowing what conditions to adjust to achieve aim grade targetproperties.

The present methods can comprise the steps of determining a first set ofoperating conditions to produce the bimodal polymer product in a firstreactor in the pilot plant with a bimodal catalyst system that includes:adjusting the ratio of the first catalyst component to the secondcatalyst component of the bimodal catalyst system; transitioning thefirst reactor from the bimodal catalyst system to a single catalystsystem under the first set of operating conditions to produce a polymercomposition; and scaling-up the production of the bimodal polymerproduct from the pilot plant to a larger production facility. Inscaling-up the production, a second reactor operates under the first setof operating conditions and utilizes the single catalyst system toproduce the polymer composition. The second reactor is transitioned fromthe single catalyst system to the bimodal catalyst system to produce thebimodal polymer product. In the second reactor, the ratio of the firstcatalyst component to the second catalyst component can be adjusted tomaintain the density and melt index of the bimodal polymer product. Inan aspect, the first set of operating conditions used to produce thepolymer composition can be modified to a second set of operatingconditions. The second set of operating conditions can be achieved inthe second reactor to produce the same density and melt index as thepolymer composition produced with the single catalyst in the pilot plantoperation. In an aspect, the second set of operating conditions can beused to produce the bimodal polymer product. In an aspect of the presentmethods, the density and the melt index of the bimodal product is notthe same as the density of the polymer composition.

Further provided are methods for scale-up from a pilot plant to a largerproduction facility of a bimodal polymer product having a density and amelt index comprising the steps of: producing a bimodal polymer productin a first reactor in a pilot plant with a bimodal catalyst system undera first set of operating conditions and producing a polymer compositionwith a single catalyst system in the first reactor under the first setof operating conditions which can be performed in either order. Thepolymer composition is produced in a second reactor in a largerproduction facility with the single catalyst system. The first set ofoperating conditions can be modified to make the polymer composition inthe second reactor under a second set of operating conditions whereinthe second set of operation conditions is achieved in the second reactorwhen the substantially same density and melt index is produced for thepolymer composition as that produced in the pilot plant. The secondreactor transitions operation from the single catalyst system to thebimodal catalyst system under the second set of operating conditions andthe amounts of the first catalyst and the second catalyst can beadjusted to produce the bimodal polymer product.

Operating conditions used in the present methods can include, but arenot limited to, an H2/C2 reactor gas ratio, a C6/C2 reactor gas ratio, aC6/C2 reactor feed ratio, reactor residence time (residence time=bedweight per polymer rate), and an isopentane concentration. The presentmethods can further comprise the step of maintaining constant oradjusting the C6/C2 reactor gas ratio and/or the C6/C2 reactor feedratio during the step of transitioning the first reactor from thebimodal catalyst system to a single catalyst system under the first setof operating conditions to produce a first polymer composition.

In an aspect, the present methods may further comprise the step ofattaining a steady state of the first reactor to determine one or morepolymer grade properties for the first polymer composition. In anaspect, the one or more polymer grade properties comprise melt index,melt index ratio and/or density. In an aspect, the polymer gradeproperties can be used to delineate a bimodal polymer composition forthe bimodal polymer product. In an aspect, the C6/C2 ratio can controlan amount of hexene incorporated into the bimodal polymer product. In anaspect, the first catalyst is a metallocene catalyst. In an aspect, thesecond catalyst is a conventional type catalyst. As provided herein, thebimodal catalyst system can include at least one metallocene catalystcomponent and at least one non-metallocene component (sometimes referredto as conventional catalyst component), or two different metallocenecatalyst components, or two conventional catalysts components. Further,the bimodal polymer product may be referred to as a multi-catalystcomposition. In an aspect, the bimodal polymer product is apolyethylene-based polymer or a polypropylene-based polymer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the present compounds, components, compositions, and/or methodsare disclosed and described, it is to be understood that unlessotherwise indicated, this invention is not limited to specificcompounds, components, compositions, reactants, reaction conditions,ligands, metallocene structures, or the like, as such may vary, unlessotherwise specified. It is also to be understood that the terminologyused herein is for the purpose of describing particular embodiments onlyand is not intended to be limiting.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a”, “an” and “the” include pluralreferents unless otherwise specified. Thus, for example, reference to “aleaving group” as in a moiety “substituted with a leaving group”includes more than one leaving group, such that the moiety may besubstituted with two or more such groups. Similarly, reference to “ahalogen atom” as in a moiety “substituted with a halogen atom” includesmore than one halogen atom, such that the moiety may be substituted withtwo or more halogen atoms, reference to “a substituent” includes one ormore substituents, reference to “a ligand” includes one or more ligands,and the like.

For the sake of brevity, only certain ranges are explicitly disclosedherein. However, ranges from any lower limit may be combined with anyupper limit to recite a range not explicitly recited, as well as, rangesfrom any lower limit may be combined with any other lower limit torecite a range not explicitly recited, in the same way, ranges from anyupper limit may be combined with any other upper limit to recite a rangenot explicitly recited. Additionally, within a range includes everypoint or individual value between its end points even though notexplicitly recited. Thus, every point or individual value may serve asits own lower or upper limit combined with any other point or individualvalue or any other lower or upper limit, to recite a range notexplicitly recited.

As used herein, the term “catalyst system” refers to at least one“catalyst component” and at least one “activator”, or, alternatively, atleast one cocatalyst. The catalyst system may also include othercomponents, such as supports, and is not limited to the catalystcomponent and/or activator alone or in combination. The catalyst systemmay include any number of catalyst components in any combination asdescribed, as well as any activator in any combination as described.

As used herein, the terms “scale-up” or “scaling-up” a polymerizationprocess refers to the steps required between an initial process designin the laboratory and completion of a final production plant (alsoreferred to herein as a “commercial plant” or a “full-scale processplant”).

The term “catalyst component” refers to any compound that, onceappropriately activated, is capable of catalyzing the polymerization oroligomerization of olefins. Preferably, the catalyst component includesat least one Group 3 to Group 12 atom and optionally at least oneleaving group bound thereto.

The term “leaving group” refers to one or more chemical moieties boundto the metal center of the catalyst component that can be abstractedfrom the catalyst component by an activator, thereby producing thespecies active towards olefin polymerization or oligomerization.Suitable activators are described in detail below.

The term “substituted” refers to the group following that term having atleast one moiety in place of one or more hydrogens in any position, themoieties selected from such groups as halogen radicals (for example, C₁,F, Br), hydroxyl groups, carbonyl groups, carboxyl groups, amine groups,phosphine groups, alkoxy groups, phenyl groups, naphthyl groups, C₁ toC₁₀ alkyl groups, C₂ to C₁₀ alkenyl groups, and combinations thereof.Examples of substituted alkyls and aryls includes, but are not limitedto, acyl radicals, alkylamino radicals, alkoxy radicals, aryloxyradicals, alkylthio radicals, dialkylamino radicals, alkoxycarbonylradicals, aryloxycarbonyl radicals, carbamoyl radicals, alkyl- anddialkyl-carbamoyl radicals, acyloxy radicals, acylamino radicals,arylamino radicals, and combinations thereof.

The terms “metallocene” or “metallocene catalyst components” are usedinterchangeably and refer to “half sandwich” and “full sandwich”compounds having one or more substituted or unsubstitutedcyclopentadienyl moiety (Cp) (typically two Cp moieties) bound to atleast one Group 3 to Group 12 metal atom, and one or more leavinggroup(s) bound to at least one metal atom.

As used herein, Cp ligands are one or more rings or ring system(s), atleast a portion of which includes 7-bonded systems, such ascycloalkadienyl ligands and heterocyclic analogues. The ring(s) or ringsystem(s) typically comprise atoms selected from the group consisting ofGroups 13 to 16 atoms, or the atoms that make up the Cp ligands areselected from the group consisting of carbon, nitrogen, oxygen, silicon,sulfur, phosphorous, germanium, boron, aluminum and combinationsthereof, wherein carbon makes up at least 50% of the ring members. Orthe Cp ligand(s) are selected from the group consisting of substitutedand unsubstituted cyclopentadienyl ligands and ligands isolobal tocyclopentadienyl, non-limiting examples of which includecyclopentadienyl, indenyl, fluorenyl and other structures. Furthernon-limiting examples of such ligands include cyclopentadienyl,cyclopentaphenanthrenyl, indenyl, benzindenyl, fluorenyl,octahydrofluorenyl, cyclooctatetraenyl, cyclopentacyclododecene,phenanthrindenyl, 3,4-benzofluorenyl, 9-phenylfluorenyl,8-H-cyclopent[a]acenaphthylenyl, 7H-dibenzofluorenyl,indeno[1,2-9]anthrene, thiophenoindenyl, thiophenofluorenyl,hydrogenated versions thereof (e.g., 4,5,6,7-tetrahydroindenyl, or“H4Ind”), substituted versions thereof, and heterocyclic versionsthereof.

The “Group 15-containing catalyst” can include Group 3 to Group 12 metalcomplexes, wherein the metal has a 2 to 8 coordinate, the coordinatingmoiety or moieties including at least two Group 15 atoms, and up to fourGroup 15 atoms. In an aspect, the Group 15-containing catalyst componentis a complex of a Group 4 metal and from one to four ligands such thatthe Group 4 metal is at least a 2 coordinate, the coordinating moiety ormoieties including at least two nitrogens. Representative Group15-containing compounds are disclosed in, for example, WO 99/01460; EPA1 0 893 454; EP A1 0 894 005; U.S. Pat. Nos. 5,318,935, 5,889,128,6,333,389 B2 and 6,271,325 B1. In an aspect, the Group 15-containingcatalyst includes Group 4 imino-phenol complexes, Group 4 bis(amide)complexes, and Group 4 pyridyl-amide complexes that are active towardsolefin polymerization to any extent.

The term “activator” refers to any compound or combination of compounds,supported or unsupported, which can activate a single-site catalystcompound (e.g., metallocenes, Group 15-containing catalysts), such as bycreating a cationic species from the catalyst component. Typically, thisinvolves the abstraction of at least one leaving group (X group in theformulas/structures above) from the metal center of the catalystcomponent. The catalyst components are thus activated towards olefinpolymerization using such activators. Examples of such activatorsinclude Lewis acids such as cyclic or oligomericpoly(hydrocarbylaluminum oxides) and so called non-coordinatingactivators (“NCA”) (alternately, “ionizing activators” or“stoichiometric activators”), or any other compound that can convert aneutral metallocene catalyst component to a metallocene cation that isactive with respect to olefin polymerization.

Lewis acids can be used to activate the metallocenes described.Illustrative Lewis acids include, but are not limited to, alumoxane(e.g., methyl alumoxane or methyl aluminoxane, “MAO”), modifiedaluminoxane (e.g., “TIBAO”), and alkylaluminum compounds. Ionizingactivators (neutral or ionic) such as tri (n-butyl)ammoniumtetrakis(pentafluorophenyl)boron may be also be used. Further, atrisperfluorophenyl boron metalloid precursor may be used. Any of thoseactivators/precursors can be used alone or in combination with theothers.

MAO and other aluminum-based activators are known in the art. Ionizingactivators are known in the art and are described by, for example,Eugene You-Xian Chen & Tobin J. Marks, Cocatalysts for Metal-CatalyzedOlefin Polymerization: Activators, Activation Processes, andStructure-Activity Relationships 100(4) Chemical Reviews 1391-1434(2000). The activators may be associated with or bound to a support,either in association with the catalyst component (e.g., metallocene) orseparate from the catalyst component, such as described by Gregory G.Hlatky, Heterogeneous Single-Site Catalysts for Olefin Polymerization100(4) Chemical REVIEWS 1347-1374 (2000).

Illustrative Ziegler-Natta catalyst compounds are disclosed in ZIEGLERCATALYSTS 363-386 (G. Fink, R. Mulhaupt and H. H. Brintzinger, eds.,Springer-Verlag 1995); or in EP 103 120; EP 102 503; EP 0 231 102; EP 0703 246; RE 33,683; U.S. Pat. Nos. 4,302,565, 5,518,973, 5,525,678,5,288,933, 5,290,745, 5,093,415 and 6,562,905. Examples of suchcatalysts include those comprising Group 4, 5, or 6 transition metaloxides, alkoxides and halides, or oxides, alkoxides and halide compoundsof titanium, zirconium or vanadium; optionally in combination with amagnesium compound, internal and/or external electron donors (alcohols,ethers, siloxanes, etc.), aluminum or boron alkyl and alkyl halides, andinorganic oxide supports.

One type of conventional-type transition metal catalysts includesZiegler-Natta catalysts currently known in the art. Other types ofconventional-type catalysts include chromium catalysts. Examples ofconventional-type transition metal catalysts are discussed in U.S. Pat.Nos. 4,115,639, 4,077,904, 4,482,687, 4,564,605, 4,721,763, 4,879,359and 4,960,741. The conventional-type transition metal catalyst compoundsthat may be used include transition metal compounds from Groups 3 to 17,or Groups 4 to 12, or Groups 4 to 6 of the Periodic Table of Elements.

These conventional-type transition metal catalysts may be represented bythe formula: MRx, where M is a metal from Groups 3 to 17, or a metalfrom Groups 4 to 6, or a metal from Group 4, or titanium; R is a halogenor a hydrocarbyloxy group; and x is the valence of the metal M. Examplesof R include alkoxy, phenoxy, bromide, chloride and fluoride. Examplesof conventional-type transition metal catalysts where M is titaniuminclude TiCl₄, TiBr₄, Ti(OC₂H₅)₃Cl, Ti(OC₂H₅)Cl₃, Ti(OC₄H₉)₃Cl,Ti(OC₃H₇)₂Cl₂, Ti(OC₂H₅)₂Br₂, TiCl₃.⅓AlCl₃ and Ti(OC₁₂H₂₅)Cl₃.

Conventional-type transition metal catalyst compounds based onmagnesium/titanium electron-donor complexes are described in, forexample, U.S. Pat. Nos. 4,302,565 and 4,302,566. Catalysts derived fromMg/Ti/Cl/THF are also contemplated, which are well known to those ofordinary skill in the art. One example of the general method ofpreparation of such a catalyst includes the following: dissolve TiCl₄ inTHF, reduce the compound to TiCl₃ using Mg, add MgCl₂, and remove thesolvent.

Conventional-type cocatalyst compounds for the above conventional-typetransition metal catalyst compounds may be represented by the formulaM₃M_(4v)X_(2c)R_(3b-c), wherein M₃ is a metal from Group 1 to 3 and 12to 13 of the Periodic Table of Elements; M₄ is a metal of Group 1 of thePeriodic Table of Elements; v is a number from 0 to 1; each X₂ is anyhalogen; c is a number from 0 to 3; each R₃ is a monovalent hydrocarbonradical or hydrogen; b is a number from 1 to 4; and wherein b minus c isat least 1. Other conventional-type organometallic cocatalyst compoundsfor the above conventional-type transition metal catalysts have theformula M₃R₃k, where M₃ is a Group IA, IIA, IIB or IIIA metal, such aslithium, sodium, beryllium, barium, boron, aluminum, zinc, cadmium andgallium; k equals 1, 2 or 3 depending upon the valency of M₃ whichvalency in turn normally depends upon the particular Group to which M₃belongs; and each R₃ may be any monovalent radical that includeshydrocarbon radicals and hydrocarbon radicals containing a Group 13 to16 element like fluoride, aluminum, oxygen or a combination thereof.

As provided herein, a bimodal catalyst system can include at least onemetallocene catalyst component and at least one non-metallocenecomponent (sometimes referred to as conventional catalyst component), ortwo metallocene catalyst components, or two conventional catalystcomponents. As used herein, multi-modal catalyst systems mean andinclude a bimodal catalyst system and a tri-modal catalyst system.Further, the bimodal polymer product may be referred to as amulti-catalyst composition.

The terms “multi-catalyst composition” and “multi-catalyst” refer to anycomposition, mixture or system that includes two or more differentcatalyst components regardless of the metals.

As described herein, the catalyst system may be supported on a carrier,typically an inorganic oxide, chloride or resinous material such as, forexample, polyethylene or silica.

Suitable metallocene catalysts particularly include the silica-supportedhafnium transition metal metallocene/methylalumoxane catalyst systemsdescribed in, for example, U.S. Pat. Nos. 6,242,545 and 6,248,845,particularly Example 1. Hafnium and zirconium transition metalmetallocene-type catalyst systems are particularly suitable. Otherparticularly suitable metallocene catalysts include those metallocenecatalysts and catalyst systems described in, U.S. Pat. Nos. 5,466,649;6,476,171; 6,225,426, and 7,951,873, and in the references citedtherein, all of which are fully incorporated herein by reference.

As provided herein, melt index is determined according to ASTM D-1238-E(190° C./2.16 kg), also sometimes referred to as I₂ or I_(2.16). A meltindex value measured with a slightly larger amount of weight is referredto as I₅, determined in the same manner as I₂, except using 5.0 kg (190°C./5.0 kg).

Flow Index is also determined according to ASTM D-1238-E but at atemperature of 190° C. using a 21.6 kg mass (i.e., 190° C./21.6 kg).

The Melt Index Ratio (“MIR”) is the ratio of I21/I2 and provides anindication of the amount of shear thinning behavior of the polymer andis a parameter that might be correlated to the overall polymer mixturemolecular weight distribution data obtained separately by using GPC andpossibly in combination with another polymer analysis including TREF.

In commercial gas phase polymerization processes, a gaseous streamcontaining one or more monomers can be passed through a fluidized bedunder reactive conditions in the presence of a catalyst. A polymerproduct is withdrawn from the reactor while fresh monomer is introducedto the reactor to replace the removed polymerized product. Unreactedmonomer and catalyst is withdrawn from the fluidized bed and recycledback to the reactor.

Commercial gas phase polymerization processes can operate in condensedmode. Condensed mode operation is achieved when a portion of the reactorcycle gas is condensed into liquids before the gas enters the bottom ofthe reactor. The reactor cycle gas is typically condensed by acombination of two things. The first is increasing the concentration ofan induced condensing agent (“ICA”), usually isopentane, to increase thecycle gas dew point temperature. The second is increasing reactor ratesto lower the temperature of the cycle gas below its dew point. Asproduction rates increase, the cycle gas cooler lowers the cycle gastemperature to offset the heat of reaction and maintain a steady reactortemperature. The combination of the higher dew point temperature and thelower cycle gas temperature leads to condensation in the cycle gas. Thecondensed liquid is vaporized in the reactor, which removes more of theheat. As such, operating in condensed mode allows otherwisecooling-limited plants to increase production rates by improving systemheat removal.

In developing a polymerization process to produce a particular grade ofpolymer product, there are a number of steps required between theinitial concept and completion of the final production plant (alsoreferred to herein as a commercial plant). These general steps includethe development of the commercial process, optimization of the process,scale-up from the bench to a pilot plant, and from the pilot plant tothe full-scale process. While the ultimate goal is to go directly fromprocess optimization to full-scale process plant, the pilot plant isgenerally a necessary step. Reasons for this critical step include:understanding the potential waste streams, examination ofmacro-processes, process interactions, process variations, processcontrols, development of standard operating procedures, etc. Theinformation developed at the pilot plant scale allows for a betterunderstanding of the overall process including side processes.Therefore, the pilot plant can help build an information base so thatthe technology can be permitted and safely implemented.

Hence, the present methodology provides a method of scaling-up apolymerization process from a pilot plant to a full-scale process plantwhere the bimodal polymer product produced in the full-scale processplant has approximately the same density, melt index, melt index ratio,and mixture concentration of a first polymer component (typically a highmolecular weight polymer) and a second polymer component (typically alower molecular weight polymer) as the bimodal polymer product that wasproduced in the pilot plant. The present methodologies are also usefulin transitioning the polymerization process from one commercial plant toanother commercial plant. The bimodal polymer product comprises a firstpolymer component and a second polymer component. The first polymercomponent is sometimes referred to as the high molecular weightcomponent. The second polymer component is sometimes referred to as thelower molecular weight component.

In the present methods, as a first step, the bimodal polymer productmeeting the end-use product requirements is produced in a pilot plantusing a bimodal catalyst system utilizing a first set of operatingconditions. The bimodal catalyst system comprises a first catalystcomponent and a second catalyst component in a ratio. In the pilotplant, the ratio of the first catalyst component to the second catalystcomponent of the bimodal catalyst system can be adjusted. A first set ofoperating conditions are used to produce the bimodal polymer product inthe pilot plant reactor (also referred to herein as a “first reactor”).The pilot plant reactor is then transitioned from the bimodal catalystsystem to a single catalyst system under the first set of operatingconditions to produce a polymer composition.

Operating conditions used to produce the bimodal polymer product caninclude, but are not limited to, a hydrogen-to-monomer gas ratio (i.e. a“H2/C2 reactor gas ratio” or “H2/C2 gas ratio”), a co-monomer/monomergas composition (i.e., a “C6/C2 mole/mole (“mol/mol”) gas composition”),a co-monomer/monomer feed ratio (i.e., a “C6/C2 feed ratio” or “C6/C2reactor feed ratio”), a reactor residence time, an inducible condensingagent (“ICA”) concentration and a residence time (i.e., a “bedweight/polymer rate”), the reactor temperature and also the ratio andamount of active catalysts. In producing the bimodal polymer product, afirst set of operating conditions are established for the bimodalpolymer product that has a particular melt index, melt index ratioand/or density.

As used herein, H2/C2 reactor gas ratio is the concentration of H2,normally measured in mol % or ppmv, depending on catalyst type, dividedby the concentration of C2, normally measured in mol %, present in thereactor cycle gas. C6/C2 reactor gas ratio is the concentration of C6,normally measured in mol %, divided by the concentration of C2, normallymeasured in mol %, present in the reactor cycle gas. C6/C2 reactor feedratio is the feed rate of C6, normally measured in kilograms or poundsper hour, divided by the feed rate of C2, normally measured in kilogramsor pounds per hour. Note that the ratio includes both fresh feeds aswell as recovered or recycled feeds if present. Reactor residence time,normally in units of hours, is defined as the bed mass, normallymeasured in tons or pounds, divided by the production rate normallymeasured in tons or pounds per hour. C2 partial pressure, normally inunits of bar or psia, is defined as the concentration of C2 in thereactor cycle gas as a mol fraction multiplied by the absolute totalreactor pressure.

Secondly, with the exception of the co-monomer-to-monomer-feed ratio,the first set of operating conditions (used to make the bimodal polymerproduct in the pilot plant) are utilized to maintain identical reactorconditions while the pilot plant reactor (referred to herein sometimesas “the first reactor”) transitions between a bimodal catalyst system toa single catalyst system to produce a first polymer composition. In thetransition to the single catalyst system, the pilot plant reactor islined out to determine the properties of the polymer made with thesingle catalyst system (sometimes referred to herein as a “unimodalcatalyst system”).

The production of the bimodal polymer product is then scaled up from thepilot plant to a full-scale process plant. The first set of operatingconditions that were developed in the pilot plant might requireadjustment during the operation in the full scale plant to develop asecond set of reactor operating conditions. To develop the second set ofoperating conditions, the first set of operating conditions as developedfrom the pilot plant is first employed with the single catalyst systemin a full-scale process plant reactor (“the second reactor” or“commercial reactor”), the polymer composition is produced and samplesof the polymer are then measured in the QC lab to determine the MI,density, MIR and whether these polymer properties are different thanwhat was produced in the pilot plant with the same single catalyst. Ifthe polymer properties in the full scale process plant differ from whatwas produced in the pilot plant at the same pilot plant reactorconditions (at the first set of operating conditions), then it isnecessary during the operation with the single catalyst system in thesecond reactor (full scale process plant) to then adjust the first setof operating conditions until the properties (MI, density and MIR) ofthe polymer are the same as the properties of the polymer produced inthe first reactor when previously using the single catalyst in the pilotplant. The final conditions, which are determined in the full scaleplant that produces essentially the same polymer properties, are definedas “a second set of operating conditions.” In summary, the final reactorconditions that are developed when the polymer properties in the fullscale process plant are essentially the same as the polymer propertiesas previously produced in the pilot plant are defined as the “second setof operating conditions.”

The second reactor then transitions from the single catalyst system tothe bimodal catalyst system to produce the bimodal polymer product underthe second set of operating conditions. If the bimodal polymer productproperties (i.e., melt index, melt index ratio and/or density) do notmatch the requirements of the bimodal polymer product produced in thepilot plant, the ratio of the first catalyst to the second catalyst ofthe bimodal catalyst system in the second reactor is adjusted.

Pilot Plants and Pilot Plant Reactor

Pilot plants are used to mimic larger production facilities orcommercial systems on a small scale. Pilot plants are cheaper to buildand cheaper to operate. Pilot plants allow an operator a less expensiveway to experiment, investigate and troubleshoot problems without therisks and expenses associated with larger scale productions. The maincycle gas stream of a pilot plant reactor can have a flow rate rangingfrom a low of about 100 lb./hr., about 15,000 lb./hr., or about 20,000lb./hr. to a high of about 25,000 lb./hr., about 30,000 lb./hr., orabout 50,000 lb./hr.

Pilot plant reactors, however, are not capable of operating in condensedmode because production rates and heat removal systems are limited.Pilot plant reactors operate with a bottom bell temperature that ishigher than commercial-scale reactors. The inlet temperature of a pilotplant reactor is typically 17° F. below reactor temperature at fullrates. This difference between the inlet temperature and reactortemperature is much lower than commercial-scale reactors, where inlettemperatures are typically about 40° F. to 85° F. below reactortemperature.

Larger Production Facilities

As used herein, the terms “larger (polymer) production facility,”“commercial scale reactor,” and “commercial reactor” are usedinterchangeably and refer to a reactor (referred to herein as a “secondreactor”) used in a full-scale process plant typically having at least adiameter of at least 14 feet, a bed height of at least 45 feet, and/or aproduction rate of at least 50,000 lbs. polymer per hour.

In a commercial reactor, the fluidized bed within the reactor housinghas the general appearance of a dense mass of individually movingparticles as created by the percolation of gas through the bed. Thepressure drop through the bed is equal to or slightly greater than theweight of the bed divided by the cross-sectional area. It is thusdependent on the geometry of the reactor housing. To maintain a viablefluidized bed in the reactor housing, the superficial gas velocitythrough the bed must exceed the minimum flow required for fluidization.Preferably, the superficial gas velocity is at least two times theminimum flow velocity. Ordinarily, the superficial gas velocity rangesfrom about 1.0 ft./sec to about 5.0 ft./sec. The superficial gasvelocity also can range from a low of about 1.0 ft./sec, about 1.5ft./sec, about 2.0 ft./sec to a high of about 3.0 ft./sec, about 4.0ft./sec, or about 5.0 ft./sec.

The amount of hydrogen in the reactor housing can be expressed as a moleratio relative to the total polymerizable monomer, for example, ethyleneor a blend of ethylene and one or more comonomers. The amount ofhydrogen used in the polymerization process can be an amount necessaryto achieve the desired flow index of the final polyolefin resin. Themole ratio of hydrogen to total monomer (hydrogen (or “H₂”): monomer)can range from 0.0001 to 0.0005; 0.001 to about 10; 0.001 to about 5;0.001 to about 3; 0.001 to about 0.10. The amount of hydrogen in thereactor housing 110 also can be 0.001 up to 3,000 ppm, 4,000 ppm, or5,000 ppm. The mole ratio of hydrogen to total monomer (H₂: monomer)also can range from 50 ppm to 5,000 ppm or 50 ppm to 2,000 ppm.

The total monomer concentration in the reactor housing can be at least20 mole %, at least 60 mole %, at least 70 mole %, at least 80 mole %,at least 90 mole %, at least 95 mole %, at least 96 mole %, at least 97mole %, at least 98 mole %, at least 99 mole %, at least 99.9 mole %, orat least 99.99 mole %. In an aspect, the reactor housing 110 can have anethylene concentration of at least 20 mole %, at least 60 mole %, atleast 70 mole %, at least 80 mole %, at least 90 mole %, at least 95mole %, at least 96 mole %, at least 97 mole %, at least 98 mole %, atleast 99 mole %, at least 99.9 mole %, or at least 99.99 mole %.

The rates are significantly less than typical commercial rates that areabout 300,000 lb./hr. or 1,000,000 lb./hr. or more.

The reaction conditions within the reactor housing vary depending uponthe monomers, catalysts and equipment availability. For example, thereaction temperature can range from about −10° C. to about 120° C., suchas about 15° C. to about 110° C. The reaction pressure can range fromabout 0.1 bar to about 100 bar, or about 5 bar to about 50 bar, forexample. The temperature and pressure of the main cycle gas streamleaving the reactor is nearly identical to that of the reactionconditions.

A cycle gas cooler can be any apparatus or system capable of decreasingthe temperature of the main cycle gas stream. The cycle gas cooler canbe used to lower the temperature of the main cycle gas by about 10° F.,about 15° F., about 20° F., or about 30° F. The cycle gas cooler can beany one or more shell-and-tube, plate and frame, plate and fin, spiralwound, coil wound, U-tube, fans, and/or bayonet style heat exchangers.Illustrative heat transfer mediums can include, but are not limited to,water, air, glycols, mixtures thereof, or the like.

A cycle gas compressor can be used to increase the pressure of thecooled main cycle gas stream exiting the cooler. The pressure of thecooled main cycle gas stream exiting the cooler can vary greatly, and istypically 10, 15, 20, or 25 psi above the reactor pressure.

Catalyst Components and Catalyst System

The methods described herein are generally directed towardpolymerization processes, particularly, gas phase processes, forpolymerizing one or more monomers in the presence of a bimodal catalystsystem.

The polymerization processes described herein may be continuousprocesses. As used herein, “a continuous process” is process thatoperates (or is intended to operate) without interruption or cessation,but may be interrupted for customary maintenance or for the occasionaldisrupting event. For example, a continuous process to produce a polymerwould be one in which the reactants are continuously introduced into oneor more reactors and polymer product is continually or semi-continuallywithdrawn.

In an aspect, the methods disclosed herein provide for a gas phaseprocess for polymerizing one or more monomer(s) in the presence of atleast one catalyst system and a condensable agent wherein the process isoperated in a condensed mode.

Illustrative Ziegler-Natta catalyst compounds are disclosed in ZIEGLERCATALYSTS 363-386 (G. Fink, R. Mulhaupt and H. H. Brintzinger, eds.,Springer-Verlag 1995); or in EP 103 120; EP 102 503; EP 0 231 102; EP 0703 246; RE 33,683; U.S. Pat. Nos. 4,302,565, 5,518,973, 5,525,678,5,288,933, 5,290,745, 5,093,415 and 6,562,905. Examples of suchcatalysts include those comprising Group 4, 5, or 6 transition metaloxides, alkoxides and halides, or oxides, alkoxides and halide compoundsof titanium, zirconium or vanadium; optionally in combination with amagnesium compound, internal and/or external electron donors (alcohols,ethers, siloxanes, etc.), aluminum or boron alkyl and alkyl halides, andinorganic oxide supports.

Conventional-type transition metal catalysts are traditionalZiegler-Natta catalysts. Examples of conventional-type transition metalcatalysts are discussed in U.S. Pat. Nos. 4,115,639, 4,077,904,4,482,687, 4,564,605, 4,721,763, 4,879,359 and 4,960,741. Theconventional-type transition metal catalyst compounds that may be usedinclude transition metal compounds from Groups 3 to 17, Groups 4 to 12,or Groups 4 to 6 of the Periodic Table of Elements.

These conventional-type transition metal catalysts may be represented bythe formula: MRx, where M is a metal from Groups 3 to 17, a metal fromGroups 4 to 6, a metal from Group 4, or titanium; R is a halogen or ahydrocarbyloxy group; and x is the valence of the metal M. Examples of Rinclude alkoxy, phenoxy, bromide, chloride and fluoride. Examples ofconventional-type transition metal catalysts where M is titanium includeTiCl₄, TiBr₄, Ti(OC₂H₅)₃Cl, Ti(OC₂H₅)Cl₃, Ti(OC₄H₉)₃Cl, Ti(OC₃H₇)₂Cl₂,Ti(OC₂H₅)₂Br₂, TiCl₃.⅓AlCl₃ and Ti(OC₁₂H₂₅)Cl₃.

Conventional-type transition metal catalyst compounds based onmagnesium/titanium electron-donor complexes are described in, forexample, U.S. Pat. Nos. 4,302,565 and 4,302,566. Catalysts derived fromMg/Ti/Cl/THF are also contemplated. One example of the general method ofpreparation of such a catalyst includes the following: dissolve TiCl₄ inTHF, reduce the compound to TiCl₃ using Mg, add MgCl₂, and remove thesolvent.

Conventional-type cocatalyst compounds for the above conventional-typetransition metal catalyst compounds may be represented by the formulaM₃M_(4v)X_(2c)R_(3b-c), wherein M₃ is a metal from Groups 1 to 3 or 12to 13 of the Periodic Table of Elements; M₄ is a metal of Group 1 of thePeriodic Table of Elements; v is a number from 0 to 1; each X₂ is anyhalogen; c is a number from 0 to 3; each R₃ is a monovalent hydrocarbonradical or hydrogen; b is a number from 1 to 4; and wherein b minus c isat least 1. Other conventional-type organometallic cocatalyst compoundsfor the above conventional-type transition metal catalysts have theformula M₃R₃k, where M₃ is a Group IA, IIA, IIB or IIIA metal, such aslithium, sodium, beryllium, barium, boron, aluminum, zinc, cadmium, orgallium; k equals 1, 2 or 3 depending upon the valency of M₃ whichvalency in turn normally depends upon the particular Group to which M₃belongs; and each R₃ may be any monovalent radical that includeshydrocarbon radicals and hydrocarbon radicals containing a Group 13 to16 element like fluoride, aluminum, oxygen or a combination thereof.

A bimodal catalyst system can be a “mixed catalyst system” and includeat least one metallocene catalyst component and at least onenon-metallocene catalyst component (referred to herein as conventionalcatalyst component). Alternatively, the mixed catalyst system caninclude two different metallocene catalyst components or two differentconventional catalyst components.

A mixed catalyst system can be described as a bimetallic catalystcomposition or a multi-catalyst composition. As used herein, the term“bimetallic catalyst” includes any composition, mixture, or system thatincludes two or more different catalyst components, each having adifferent metal group. The terms “multi-catalyst composition” and“multi-catalyst” include any composition, mixture, or system thatincludes two or more different catalyst components regardless of themetals. Therefore, the terms “bimetallic catalyst composition,”“bimetallic catalyst,” “multi-catalyst composition,” “multi-catalyst,”and “bimodal” can be collectively referred to as a “mixed catalystsystem.”

The bimodal catalyst system may be supported on a carrier, typically aninorganic oxide or chloride or a resinous material such as, for example,polyethylene or silica.

Suitable metallocene catalysts particularly include the silica-supportedhafnium transition metal metallocene/methylalumoxane catalyst systemsdescribed in, for example, U.S. Pat. Nos. 6,242,545 and 6,248,845,Example 1. Hafnium and zirconium transition metal metallocene-typecatalyst systems are particularly suitable. Other particularly suitablemetallocene catalysts include those metallocene catalysts and catalystsystems described in, U.S. Pat. Nos. 5,466,649, 6,476,171, 6,225,426,and 7,951,873.

Different catalysts including conventional-type transition metalcatalysts are suitable for use in the polymerization processes of themethods disclosed herein. The following is a non-limiting discussion ofthe various polymerization catalysts useful. All numbers and referencesto the Periodic Table of Elements are based on the new notation as setout in Chemical and Engineering News, 63(5), 27 (1985), unless otherwisespecified.

The transition metal compound may be described as a catalyst precursor,a transition metal catalyst, a polymerization catalyst, or a catalystcompound, and these terms are used interchangeably. The term activatoris used interchangeably with the term co-catalyst. As used herein, “atleast one catalyst system” refers to a combination comprising a catalystcompound and an activator capable of polymerizing monomers.

Conventional Catalysts

Conventional catalysts refer to Ziegler-Natta catalysts or Phillips-typechromium catalysts. Examples of conventional-type transition metalcatalysts are discussed in U.S. Pat. Nos. 4,115,639, 4,077,9044,482,687, 4,564,605, 4,721,763, 4,879,359 and 4,960,741. Theconventional catalyst compounds that may be used in the processesdisclosed herein include transition metal compounds from Groups 3 to 10,preferably 4 to 6 of the Periodic Table of Elements.

These conventional-type transition metal catalysts may be represented bythe formula:

MRx  (I),

where M is a metal from Groups 3 to 10, Group 4, or titanium; R is ahalogen or a hydrocarbyloxy group; and x is the valence of the metal M,preferably x is 1, 2, 3 or 4, or x is 4. Non-limiting examples of Rinclude alkoxy, phenoxy, bromide, chloride and fluoride. Non-limitingexamples of conventional-type transition metal catalysts where M istitanium include TiCl3, TiCl4, TiBr4, Ti(OC2H5)3Cl, Ti(OC2H5)Cl3,Ti(OC4H9)3Cl, Ti(OC3H7)2Cl2, Ti(OC2H5)2Br2, TiC3.⅓AlCl3 andTi(OC12H25)Cl3.

Conventional chrome catalysts, often referred to as Phillips-typecatalysts, may include CrO3, chromocene, silyl chromate, chromylchloride (CrO2Cl2), chromium-2-ethyl-hexanoate, chromium acetylacetonate(Cr(AcAc)3). Non-limiting examples are disclosed in U.S. Pat. Nos.2,285,721, 3,242,099 and 3,231,550.

For optimization, many conventional-type catalysts require at least onecocatalyst. A detailed discussion of cocatalysts may be found in U.S.Pat. No. 7,858,719, col. 6, line 46, bridging col. 7, line 45.

Metallocene Catalysts

Polymerization catalysts useful in the present methods include one ormore metallocene compounds (also referred to herein as metallocenes ormetallocene catalysts). Metallocene catalysts are generally described ascontaining one or more ligands and one or more leaving groups bonded toat least one metal atom, optionally with at least one bridging group.The ligands are generally represented by one or more open, acyclic, orfused ring(s) or ring system(s) or a combination thereof. These ligands,preferably the ring(s) or ring system(s) are typically composed of oneor more atoms selected from Groups 13 to 16 atoms of the Periodic Tableof Elements; alternatively, the atoms may be selected from the groupconsisting of carbon, nitrogen, oxygen, silicon, sulfur, phosphorous,germanium, boron and aluminum or a combination thereof. The ring(s) orring system(s) may be composed of carbon atoms such as, but not limitedto, those cyclopentadienyl ligands or cyclopentadienyl-type ligandstructures or other similar functioning ligand structures such as apentadiene, a cyclooctatetraendiyl, or an imide ligand. The metal atommay be selected from Groups 3 through 15 and the lanthanide or actinideseries of the Periodic Table of Elements. Alternatively, the metal maybe a transition metal from Groups 4 through 12, alternatively Groups 4,5 and 6, alternatively the transition metal is from Group 4.

Metallocene catalysts and catalyst systems are described in for example,U.S. Pat. Nos. 4,530,914, 4,871,705, 4,937,299, 5,017,714, 5,055,438,5,096,867, 5,120,867, 5,124,418, 5,198,401, 5,210,352, 5,229,478,5,264,405, 5,278,264, 5,278,119, 5,304,614, 5,324,800, 5,347,025,5,350,723, 5,384,299, 5,391,790, 5,391,789, 5,399,636, 5,408,017,5,491,207, 5,455,366, 5,534,473, 5,539,124, 5,554,775, 5,621,126,5,684,098, 5,693,730, 5,698,634, 5,710,297, 5,712,354, 5,714,427,5,714,555, 5,728,641, 5,728,839, 5,753,577, 5,767,209, 5,770,753,5,770,664; EP-A-0 591 756, EP-A-0 520-732, EP-A-0 420 436, EP-B1 0 485822, EP-B1 0 485 823, EP-A2-0 743 324, EP-B1 0 518 092; WO 91/04257, WO92/00333, WO 93/08221, WO 93/08199, WO 94/01471, WO 96/20233, WO97/15582, WO 97/19959, WO 97/46567, WO 98/01455, WO 98/06759, and WO98/011144.

Mixed Catalysts

As noted above, the bimodal catalyst system can include at least onemetallocene catalyst component and at least one non-metallocenecomponent (sometimes referred to as conventional catalyst component), ortwo metallocene catalyst components, or two conventional catalystscomponents. As used herein, multi-modal catalyst systems mean andinclude a bimodal catalyst system or a tri-modal catalyst system.Further, the bimodal polymer product may be referred to as amulti-catalyst composition.

In an aspect of the methods disclosed herein, at least one catalystsystem may comprise a mixed catalyst, i.e., two or more of the same ordifferent types of catalysts, such as the ones described above. Forexample, a metallocene catalyst may be combined with one or moreconventional catalysts or advanced catalysts.

Activator and Activation Methods

The above described polymerization catalysts, particularly, metallocenecatalysts, are typically activated in various ways to yieldpolymerization catalysts having a vacant coordination site that willcoordinate, insert, and polymerize olefin(s).

As used herein, the term “activator” refers to any compound that canactivate any one of the polymerization catalyst compounds describedherein by converting the neutral polymerization catalyst compound to acatalytically active catalyst cation compound. Non-limiting activators,for example, include alumoxane, aluminum alkyls, ionizing activators,which may be neutral or ionic, and conventional-type cocatalysts. Adetailed discussion of activators and activation methods may be found inU.S. Pat. No. 7,858,719, col. 14, line 21, bridging col. 17, line 30.

Method for Supporting

The above described catalysts and catalyst systems may be combined withone or more support materials or carriers using a support method. In anaspect, the at least one catalyst system is in a supported form.

As used herein, the terms “support” or “carrier” are usedinterchangeably and are any porous or non-porous support material, andmay be a porous support material, for example, talc, inorganic oxidesand inorganic chlorides, for example silica or alumina. Other carriersinclude resinous support materials such as polystyrene, a functionalizedor crosslinked organic supports, such as polystyrene divinyl benzenepolyolefins or polymeric compounds, or any other organic or inorganicsupport material and the like, or mixtures thereof.

The preferred carriers are inorganic oxides that include those Group 2,3, 4, 5, 13 or 14 metal oxides. The preferred supports include silica,alumina, silica-alumina, magnesium chloride, and mixtures thereof. Otheruseful supports include magnesia, titania, zirconia, montmorillonite andthe like. Combinations of these support materials may be used, such as,silica-chromium and silica-titania.

Examples of supported metallocene catalyst systems are described in U.S.Pat. Nos. 4,701,432, 4,808,561, 4,912,075, 4,925,821, 4,937,217,5,008,228, 5,238,892, 5,240,894, 5,332,706, 5,346,925, 5,422,325,5,466,649, 5,466,766, 5,468,702, 5,529,965, 5,554,704, 5,629,253,5,639,835, 5,625,015, 5,643,847, 5,648,310, 5,665,665, 5,698,487,5,714,424, 5,723,400, 5,723,402, 5,731,261, 5,743,202, 5,759,940,5,767,032, 5,688,880, 5,770,755 and 5,770,664; WO 95/32995, WO 95/14044,WO 96/06187, WO96/11960, and WO96/00243.

Examples of supported conventional catalyst systems are described inU.S. Pat. Nos. 4,894,424, 4,376,062, 4,395,359, 4,379,759, 4,405,495,4,540,758 and 5,096,869.

Polymerization Process

At least one of the catalyst systems described above is suitable for usein any gas phase polymerization process, including fluidized bed orstirred bed processes, and the gas phase polymerization process may beone in which one or more condensable agents as described below areutilized.

The catalyst feed may be introduced as pre-formed particles in one ormore liquid carriers (i.e., a catalyst slurry). Suitable liquid carrierscan include mineral oil or be combined with special types of gels toimprove the stability of the slurry to minimize the rate of solidsettling, and/or liquid or gaseous hydrocarbons including, but notlimited to, propane, butane, isopentane, hexene, heptane, octane, ormixtures thereof. A gas that is inert to the catalyst slurry such as,for example, nitrogen or argon can also be used to carry the catalystslurry into the reactor. In an aspect, the catalyst can be a dry powder.In an aspect, the catalyst can be dissolved in a liquid carrier andintroduced to the reactor as a solution.

Typically, in a gas phase polymerization process, a continuous cycle isemployed where in one part of the cycle of a reactor system, a cyclinggas stream, otherwise known as a recycle stream or fluidizing medium, isheated in the reactor by the heat of polymerization. This heat isremoved from the recycle composition in another part of the cycle by acooling system external to the reactor. Generally, in a gas fluidizedbed process for producing polymers, a gaseous stream containing one ormore monomers is continuously cycled through a fluidized bed in thepresence of at least one catalyst system under polymerizable conditions.As used herein, “polymerizable conditions” refers to any and all processconditions and any and all equipment necessary and suitable topolymerize olefins into polyolefins. In an aspect, a condensable agentas described below, is introduced to the process for purposes ofincreasing the cooling capacity of the recycle stream. The purposefulintroduction of a condensable agent into a gas phase process is referredto as a “condensed mode process” discussed in greater detail below. Thegaseous stream is withdrawn from the fluidized bed and recycled backinto the reactor. Simultaneously, polymer product is withdrawn from thereactor and fresh reactants including monomers are added to the reactor.See, for example, U.S. Pat. Nos. 4,543,399, 4,588,790, 5,028,670,5,317,036, 5,352,749, 5,405,922, 5,436,304, 5,453,471, 5,462,999,5,616,661 and 5,668,228.

Condensable Agent(s)

Condensable agents or fluids generally include hydrocarbons havinglittle to no solvent power regarding the polymer product(s). Suitablecondensing agents include C4-C8 hydrocarbons and mixtures thereof,preferably C4-C6 hydrocarbons and mixtures thereof, including linear,branched, cyclic, substituted hydrocarbons, as well as their respectiveisomers.

Condensed Mode Process

The condensing agent may be used in a gas phase polymerization processor simply a gas phase process. The gas phase process is operated in acondensed mode where a condensing agent as described above is introducedto the process to increase the cooling capacity of the recycle stream.The gas phase process is particularly well-suited for polymerizing oneor more olefin(s), at least one of which may be ethylene or propylene,in a fluidized bed reactor, the process operating in a condensed mode inwhich a liquid and a gas are introduced to the fluidized bed reactorhaving a fluidizing medium or a stirred bed reactor having a medium,wherein the level of condensable fluid, is greater than 5 weightpercent, alternatively, greater than 10 weight percent, or greater than15 weight percent or greater than 20 weight percent, alternativelygreater than 25 weight percent, alternatively greater than 30 weightpercent, alternatively greater than 35 weight percent, and alternativelygreater than 30 weight percent up to 60 weight percent, alternatively 50weight percent, 55 weight percent, 60 weight percent, 65 weight percent,70 weight percent, 75 weight percent, 80 weight percent, 85 weightpercent, 90 weight percent, 91 weight percent, 92 weight percent, 95weight percent, 96 weight percent, 97 weight percent, 98 weight percent,or 99 weight percent, based on the total weight of the liquid and gasentering the reactor. For further details of a condensed mode processsee, for example, U.S. Pat. Nos. 5,342,749 and 5,436,304.

In an aspect, the methods disclosed herein are directed to a process,preferably a continuous process, for polymerizing monomer(s) in areactor, said process comprising the steps of: (a) introducing a recyclestream into the reactor, the recycle stream comprising one or moremonomer(s); (b) introducing a polymerization catalyst and a condensablefluid into the reactor; (c) withdrawing the recycle stream from thereactor; (d) cooling the recycle stream to form a gas phase and a liquidphase; (e) reintroducing the gas phase and the liquid phase into thereactor; (f) introducing into the reactor additional monomer(s) toreplace the monomer(s) polymerized; and (g) withdrawing a polymerproduct from the reactor. In an aspect, the condensable fluid isintroduced in amounts greater than 10 weight percent or greater than 15weight percent or greater than 20 weight percent, alternatively greaterthan 25 weight percent, alternatively greater than 30 weight percent orgreater than 35 weight percent, and alternatively greater than 40 weightpercent based on the total weight of fluidizing medium beingreintroduced into the reactor.

Reactor Conditions

The reactor pressure in any of the gas phase processes described abovevaries from about 100 psig (690 kPa) to about 500 psig (3448 kPa),alternatively, in the range of from about 200 psig (1379 kPa) to about400 psig (2759 kPa), and alternatively in the range of from about 250psig (1724 kPa) to about 350 psig (2414 kPa).

The reactor temperature in any of the gas phase processes describedabove varies from about 30° C. to about 120° C., alternatively fromabout 60° C. to about 115° C., alternatively in the range of from about70° C. to 110° C., and alternatively in the range of from about 70° C.to about 100° C. In an aspect, the polymerization temperature is aboveambient temperature (23° C.), alternatively above 30° C., alternativelyabove 50° C., alternatively above 70° C.

The methods disclosed herein can produce greater than 1 lbs. of polymerper hour (0.454 Kg/hr.) to about 200,000 lbs./hr. (90,900 Kg/hr.) orhigher of polymer, alternatively greater than 1000 lbs./hr. (455Kg/hr.), alternatively greater than 10,000 lbs./hr. (4540 Kg/hr.),alternatively greater than 25,000 lbs./hr. (11,300 Kg/hr.),alternatively greater than 35,000 lbs./hr. (15,900 Kg/hr.),alternatively greater than 100,000 lbs./hr. (45,500 Kg/hr.), andalternatively greater than 65,000 lbs./hr. (29,000 Kg/hr.) to greaterthan 200,000 lbs./hr. (90,700 Kg/hr.).

Monomers and Polymers

Polymers produced in accordance with the methods disclosed herein areolefin polymers or “polyolefins”. As used herein, “olefin polymers” or“polyolefins” refers to at least 75 mole % of the polymer is derivedfrom hydrocarbon monomers, alternatively at least 80 mole %,alternatively at least 85 mole %, alternatively at least 90 mole %,alternatively at least 95 mole %, and alternatively at least 99 mole %.Hydrocarbon monomers are monomers made up of only carbon and hydrogen.For example, the monomers to be polymerized are aliphatic or alicyclichydrocarbons (as defined under “Hydrocarbon” in Hawley's CondensedChemical Dictionary, 13th edition, R. J. Lewis ed., John Wiley and Sons,New York, 1997). In an aspect, the monomers to be polymerized are linearor branched alpha-olefins, alternatively C2 to C40 linear or branchedalpha-olefins, alternatively C2 to C20 linear or branched alpha-olefins,e.g., ethylene, propylene, butene, pentene, hexene, heptene, octene,nonene, decene, undecene, dodecene, or mixtures thereof. Well-suitedmonomers include two or more olefin monomers of ethylene, propylene,butene-1, pentene-1,4-methyl-pentene-1, hexene-1, octene-1, decene-1,and mixtures thereof.

Other monomers include ethylenically unsaturated monomers, diolefinshaving 4 to 18 carbon atoms, conjugated or nonconjugated dienes,polyenes, vinyl monomers and cyclic olefins. Non-limiting monomersinclude butadiene, norbornene, norbornadiene, isobutylene,vinylbenzocyclobutane, ethylidene norbornene, isoprene,dicyclopentadiene and cyclopentene.

In an aspect, ethylene or propylene is polymerized with at least twodifferent comonomers, optionally, one of which may be a diene, to form aterpolymer.

The polymers produced by the methods disclosed herein are useful inmaking a wide variety of products and useful in many end-useapplications. The polymers include low density polyethylenes, linear lowdensity polyethylenes, medium density polyethylenes, and high densitypolyethylenes.

The polymers produced, typically polyethylene polymers, may have adensity in the range of from 0.860 g/cc to 0.970 g/cc, alternatively inthe range of from 0.880 g/cc to 0.965 g/cc, alternatively in the rangeof from 0.900 g/cc to 0.960 g/cc, alternatively in the range of from0.905 g/cc to 0.950 g/cc, alternatively in the range from 0.910 g/cc to0.940 g/cc, and alternatively greater than 0.912 g/cc.

In an aspect, the polymers produced by the methods disclosed hereintypically have a molecular weight distribution, a weight averagemolecular weight to number average molecular weight (Mw/Mn) of about 1.5to about 30, particularly about 2 to about 15, alternatively about 2 toabout 10, alternatively about 2.2 to less than about 8, andalternatively from about 2.5 to about 8. The ratio of Mw/Mn is measuredby gel permeation chromatography techniques.

In an aspect, the polyethylene polymers typically have a narrow or broadcomposition distribution as measured by Composition Distribution BreadthIndex (CDBI). See, for example, WO 93/03093. CDBIs may be generally inthe range of greater than 50% to 99%, alternatively in the range of 55%to 85%, and alternatively 60% to 80%, alternatively greater than 60%,and alternatively greater than 65%. Alternatively, CDBIs may begenerally less than 50%, alternatively less than 40%, and alternativelyless than 30%.

Polyethylene polymers may have a melt index (MI) or (I2) as measured byASTM-D-1238-E in the range from 0.01 dg/min to 1000 dg/min,alternatively from about 0.01 dg/min to about 100 dg/min, alternativelyfrom about 0.1 dg/min to about 50 dg/min, and alternatively from about0.1 dg/min to about 10 dg/min. The polyethylene polymers may have a meltindex ratio (I21.6/I2.16 or for shorthand “121/12”) (measured byASTM-D-1238-F) of from 10 to less than 25, alternatively from about 15to less than 25. Further, in an aspect, the polymers have a melt indexratio (I21/I2) of greater than 25, alternatively greater than 30,alternatively greater than 40, alternatively greater than 50 andalternatively greater than 65. Alternatively, the polyethylene polymersmay have a melt index ratio (I21/I2) in the range of from 15 to 40,alternatively in the range of from about 20 to about 35, alternativelyin the range of from about 22 to about 30, and alternatively in therange of from 24 to 27.

In an aspect, propylene polymers (referred to also as propylene-basedpolymers) may be produced. These polymers include without limitationatactic polypropylene, isotactic polypropylene, and syndiotacticpolypropylene. Other propylene polymers include propylene random, blockor impact copolymers.

Polymers produced are useful in forming a variety of articles. Sucharticles include without limitation films, sheets, and fibers. Thearticles may be produced by extrusion and co-extrusion as well as blowmolding, injection molding, and rotational molding. Films include blownor cast films formed by coextrusion or by lamination, shrink films,cling films, stretch films, sealing films, and oriented films. The filmsare useful in packaging, heavy duty bags, grocery sacks, food packaging,medical packaging, industrial liners, geo-membranes, etc. Fibers includemelt spinning, solution spinning and melt blown fiber operations for usein woven or non-woven form to make filters, diaper fabrics, medicalgarments, geotextiles, etc. Extruded articles include medical tubing,wire and cable coatings, geomembranes, and pond liners. Molded articlesinclude single and multi-layered constructions in the form of bottles,tanks, large hollow articles, rigid food containers, playgroundequipment, toys, etc.

It is to be understood that while the invention has been described inconjunction with the specific embodiments thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention. An aspect, advantages and modifications will be apparent tothose skilled in the art to whom the invention pertains.

Therefore, the following prophetic example is put forth so as to providethose skilled in the art with a complete disclosure and description andare not intended to limit the scope of that which the inventors regardas their invention.

Prophetic Example I

In this prophetic example, a set of operating conditions is firstdetermined in a pilot plant using a bimodal catalyst system to achievepolymer composition having a particular melt index and density. Thepilot plant is then transitioned from a bimodal catalyst system to asingle catalyst system and product runs are performed to produce productwith similar melt index and density and at a similar temperature as inthe bimodal catalyst system. Tables 1A and 1B include exemplaryoperating conditions and other parameters that can be used to implementthe methodologies described herein.

Subsequently, in a commercial reactor scale-up trial, the same singlecatalyst system used in the pilot plant run is running (Column 3 ofTable 1A). In the commercial reactor, the operating conditions are thenadjusted to match the operating conditions of single catalyst system inthe pilot plant (Column 4 of Table 1B). The commercial reactor is thentransitioned to a bimodal catalyst system at similar operatingtemperatures of the pilot plant to achieve a product having a similarmelt index and density as shown in Column 5 and 6 of Table 1B.

More specifically, as provided in Table 1A and Table 1B below, the firstcolumn (referred to as column 1) shows the operation of the bimodalcatalyst system in the pilot plant to produce the desired 1MI, 0.920gm/cc density and 40 MIR for the bimodal polymer product. The bimodalcatalyst system is fed to the reactor in an oil slurry and mixed withadditional B catalyst and fed as a solution to provide a final 45% A,55% B catalyst mixture feeding the reactor. Together with the catalystratio adjustments, operating conditions are adjusted as shown in column1 to produce the desired bimodal polymer product properties.

After defining the operating conditions that make the targeted bimodalpolymer product (column 1), the pilot plant reactor is transitioned tousing a single catalyst system (column 2). The bimodal catalyst systemas feed slurry as well as extra B catalyst feed is decreased until bothare shut-off. The single catalyst starts feeding the first reactor andeventually it is the only catalyst that feeds the reactor. The reactorconditions are maintained the same in column 2 as also shown incolumn 1. At these conditions the single catalyst makes differentpolymer properties compared to the polymer properties of the bimodalpolymer product. The polymer properties obtained with the singlecatalyst are used as targets when later the single catalyst is used inthe commercial plant.

Scaling-up to the commercial plant, the sequence begins with theoperation as shown by column 3 with the single catalyst. To begin,column 3 shows the use of the same conditions as shown in column 1 and 2(from the pilot plant). However, it is expected that the commercialplant will have offsets compared to the pilot plant so column 3 showsthat the properties are different in the commercial plant as compared towhat was observed in the pilot plant.

TABLE 1A 1 2 3 Reactor Pilot Plant Pilot Plant Commercial Catalyst TypeBimodal Single Single Catalyst Catalyst Catalyst Base Bimodal Bimodal PEUse single Use same Catalyst production catalyst at conditions as sameconditions pilot plant as bimodal (column 2) (column 1) % A 50  n/a* n/a% B 50 n/a n/a Added B Catalyst Yes No No Final Catalyst delivered toreactor % A 45 n/a n/a % B 55 n/a n/a Single Catalyst No Yes Yes feed toreactor Reactor 82 82 82 Temperature, ° C. Reactor Pressure, 300 300 300psia Hexene-1/Ethylene 0.08 0.08 0.08 feed ratio, lb/lb H2/C2 Reactor 55 5 gas ratio, ppm/mole % Polymer Properties Melt Index, MI, 1 2.5 1.9gm/10 minute Density, gm/cc 0.920 0.918 0.921 Melt Index Ratio 40 35 34

While continuing to use the single catalyst system, Column 4 of Table 1Bbelow shows how the reactor conditions are adjusted to make the samepolymer properties as were produced in the pilot plant (Column 2 ofTable 1A).

Next the commercial reactor (second reactor) is transitioned to thebimodal catalyst at the same conditions as shown by Column 5 (Table 1B),and this sets the conditions needed to make the bimodal polymer product.Column 5 of Table 1B however shows that the polymer properties of thebimodal polymer product are different than the target properties thatwere produced in the pilot plant (column 1).

Column 6 of Table 1B shows how the catalyst ratio is adjusted to changethe polymerpropertiestomatchthepropertiesofthepolymerasmadeinthepilotplant (column 1). Alternatively, if the H2/C2 or C6/C2 were changedinstead of the catalyst ratio, then the bimodal polymer product wouldhave made a different bimodal polymer versus the targeted properties.

TABLE 1B 4 5 6 Reactor Commercial Commercial Commercial Catalyst SingleBimodal Bimodal Catalyst Catalyst Catalyst Base Bimodal Adjust RunBimodal Adjust catalyst Catalyst conditions Catalyst at ratio to get tomatch same conditions aim grade for pilot plant developed by bimodalcatalyst properties single catalyst to match pilot (column 3) (column 4)plant bimodal product (column 1) % A n/a 50 50 % B n/a 50 50 Added BCatalyst No Yes Yes Final Catalyst delivered to reactor % A n/a 45 40 %B n/a 55 60 Single Catalyst Yes feed to reactor Reactor 82 82 82Temperature, ° C. Reactor Pressure, 300 300 300 psia Hexene-1/Ethylene0.10 0.10 0.10 feed ratio, lb/lb H2/C2 Reactor gas 5.5 5.5 5.5 ratio,ppm/mole % Polymer Properties Melt Index, MI, 2.5 0.8 1 gm/10 minuteDensity, gm/cc 0.918 0.917 0.920 Melt Index Ratio 35 37 40

All priority documents are herein fully incorporated by reference forall jurisdictions in which such incorporation is permitted and to theextent such disclosure is consistent with the description of the presentinvention. Further, all documents and references cited herein, includingtesting procedures, publications, patents, journal articles, etc. areherein fully incorporated by reference for all jurisdictions in whichsuch incorporation is permitted and to the extent such disclosure isconsistent with the description of the present invention.

While the invention has been described with respect to a number ofaspects and examples, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope and spirit of the invention as disclosedherein.

We claim:
 1. A method for scale-up from a pilot plant to a largerproduction facility of a bimodal polymer product having a density and amelt index comprising the steps of: determining a first set of operatingconditions to produce the bimodal polymer product in a first reactor inthe pilot plant with a bimodal catalyst system, wherein the bimodalcatalyst system comprises a first catalyst component and a secondcatalyst component in a ratio; adjusting the ratio of the first catalystcomponent to the second catalyst component of the bimodal catalystsystem; transitioning the first reactor from the bimodal catalyst systemto a single catalyst system under the first set of operating conditionsto produce a polymer composition; scaling-up the production of thebimodal polymer product from the pilot plant to a larger productionfacility under the first set of operating conditions, wherein the largerproduction facility has a second reactor utilizing the single catalystsystem; and transitioning the second reactor from the single catalystsystem to the bimodal catalyst system to produce the bimodal polymerproduct.
 2. The method of claim 1, wherein the ratio of the firstcatalyst component to the second catalyst component is adjusted tomaintain the density and melt index of the bimodal polymer product. 3.The method of claim 1, wherein the first set of operating conditions areadjusted to a second set of operating conditions to produce the polymercomposition.
 4. The method of claim 1, wherein the density, the meltindex and/or the melt index ratio of the bimodal product is not the samethe density, the melt index and/or the melt index ratio of the polymercomposition made with the single catalyst system.
 5. A method forscale-up from a pilot plant to a larger production facility of a bimodalpolymer product having a density and a melt index comprising the stepsof: producing a bimodal polymer product in a first reactor in a pilotplant with a bimodal catalyst system under a first set of operatingconditions, wherein the bimodal catalyst system comprises a firstcatalyst component and a second catalyst component; producing a polymercomposition in a second reactor in a larger production facility with thesingle catalyst system; modifying the first set of operating conditionsto make the polymer composition in the second reactor wherein a secondset of operating conditions are determined; transitioning the secondreactor from the single catalyst system to the bimodal catalyst systemunder the second set of operating conditions; and adjusting the amountsof the first catalyst component and the second catalyst component toproduce the bimodal polymer product.
 6. The method of claim 5, furthercomprising the step of producing the polymer composition with a singlecatalyst system in the first reactor under the first set of operatingconditions;
 7. A method for scale-up from a first reactor to a secondreactor to produce a bimodal polymer product having a density and a meltindex comprising the steps of: determining a first set of operatingconditions to produce the bimodal polymer product in a first reactorwith a bimodal catalyst system, wherein the bimodal catalyst systemcomprises a first catalyst component and a second catalyst component ina ratio; adjusting the ratio of the first catalyst component to thesecond catalyst component of the bimodal catalyst system; transitioningthe first reactor from the bimodal catalyst system to a single catalystsystem under the first set of operating conditions to produce a polymercomposition; scaling-up the production of the bimodal polymer productfrom the first reactor to the second reactor under the first set ofoperating conditions, wherein the second reactor has a second reactorutilizing the single catalyst system; and transitioning the secondreactor from the single catalyst system to the bimodal catalyst systemto produce the bimodal polymer product.
 8. The method of claim 7,wherein the first reactor and/or the second reactor is a gas phasereactor.
 9. The method of claim 1, wherein the first set of operatingconditions includes one or more of the following: a H2/C2 reactor gasratio; a C6/C2 reactor feed ratio; a reactor residence time, wherein thereactor residence time is weight of polymer in the reactor divided byproduction rate of bimodal polymer product; and an induced condensingagent (ICA) concentration.
 10. The method of claim 5, wherein the firstset of operating conditions includes one or more of the following: aH2/C2 reactor gas ratio; a C6/C2 reactor feed ratio; a reactor residencetime, wherein the reactor residence time is weight of polymer in thereactor divided by production rate of bimodal polymer product; and aninduced condensing agent (ICA) concentration.
 11. The method of claim 7,wherein the first set of operating conditions includes one or more ofthe following: a H2/C2 reactor gas ratio; a C6/C2 reactor feed ratio; areactor residence time, wherein the reactor residence time is weight ofpolymer in the reactor divided by production rate of bimodal polymerproduct; and an induced condensing agent (ICA) concentration. 12.(canceled)
 13. The method of claim 1, further comprising the step ofadjusting a C6/C2 reactor gas ratio and/or C6/C2 reactor feed ratioduring the step of transitioning the first reactor from the bimodalcatalyst system to a single catalyst system under the first set ofoperating conditions to produce a first polymer composition.
 14. Themethod of claim 1, wherein the first catalyst component and/or thesecond catalyst component is a metallocene catalyst.
 15. The method ofclaim 1, wherein the first catalyst component and/or second catalystcomponent is a conventional-type catalyst.
 16. The method of claim 1,wherein the single catalyst system comprises a conventional typecatalyst or a metallocene catalyst.
 17. The method of claim 1, whereinthe bimodal polymer product is selected from a polyethylene-basedpolymer composition and a polypropylene-based polymer composition. 18.(canceled)
 19. The method of claim 17, wherein the bimodal polymerproduct is a linear low density polyethylene-based polymer composition.20. The method of claim 1, wherein the first reactor and/or the secondreactor is a gas phase reactor, a solution phase reactor, a highpressure reactor and/or a slurry reactor.
 21. The method of claim 1,wherein the bimodal catalyst system comprises a metallocene catalyst anda conventional-type catalyst or two different metallocene catalysts. 22.The method of claim 20, wherein the first reactor and/or the secondreactor is a gas phase reactor, the same or different gas phase reactor.